Hey Tim, i have checked it out in 10m weather and it looked pretty smooth, but not sure if it will be smooth enough for your speed runs. Try putting a post up on the Windsurfing SA forums on Seabreeze, there are a few windsurfers that sail down there that kite as well. They will probably give you some more detailed info.
Cheers Croc

PS, for the new crew, this spot is completely off shore and not recommmended for anyone but experienced kiters only.